Abstract Adolescents and young adults (AYA) aged 14-24 years with HIV in Africa experience substantially higher rates of viral failure and HIV-related mortality as compared to adults. Thus, effective public health strategies tailored for and tested in this age group are urgently needed. The physical, psychological and social transitions faced by AYA create unique susceptibilities to prevalent and formidable structural (e.g., transport costs), psychosocial (e.g., the desire to fit in with peers, stigma) and clinic-based (e.g., unfriendly providers, long waiting times) barriers to engagement in public health HIV treatment settings. The variability in the intensity and the nature of barriers, however, poses a critical challenge: if barriers are highly variable, then no individual interventions are needed by all, while they also fail to help all in need. Adaptive strategies represent a novel approach to such problems with no ?silver-bullet? solutions, and which we hypothesize have particular relevance for engagement of AYA in HIV treatment. Adaptive strategies typically begin with a less intensive intervention, and then escalate to a more intensive intervention only in those not doing well. Maintaining lower-intensity interventions in those doing well conserves resources in the substantial fraction of AYA who do not need additional services, thereby enabling more intensive support for those in need. While sequential multiple assignment randomized trials (SMARTs), which are used to compare different sequences of interventions, have been used to study mental illness, cancer therapy and HIV treatment, this proposal is the first to apply a SMART to address engagement of AYA in HIV treatment in Africa. Within this design, we will use developmentally appropriate interventions with high potential for effectiveness that will be tailored by AYA pre-implementation. Specifically, we will randomize 880 AYA with HIV in Kenya to either (1) youth-centered education & counseling (standard of care) vs. (2) addition of a SMS and peer electronic navigator who provides support, information and counseling via phone. Those with a lapse in engagement will be re-randomized a second time to one of three higher-intensity re- engagement interventions: (1) standard of care outreach and intensified counseling, (2) conditional cash transfers and (3) in-person peer navigation. The primary outcome will be a combination of visit adherence and viral load suppression. This study will quantify the relative effectiveness (and cost effectiveness) of several strategies composed of promising individual interventions. We will assess provider and patient experiences and satisfaction with the interventions using mixed methods. This innovative study will offer relevant evidence for public health programming to end the AIDS epidemic for AYA with HIV.